So this is the second time I've been woken up at night by a pretty loud, high frequency whirring sound outside the house. It's the kind of sound some people would probably choose to interpret as a UFO (I'll have to admit it kinda sounds like the UFO sound we're familiar with from movies and stuff, which means it has to be something that can somehow be created by humans), but I'm looking for a logical explanation.

Is it a car engine? Electricity? A far away train? Some natural phenomena? Both times I've heard the sound during the middle of the night and it lasts about a minute before it disappears.

Except it was louder (loud enough to wake me up), the frequency was higher and it was a less 'clean', more distorted kind of sound.

I've ruled out trains, because I did hear some trains but they were further away and easily recognizable and their sound should have been transformed dramatically for them to sound like that. I'd have said jets but we get those all the time and usually you don't hear them.

I just found out they are testing out a new sort of unmanned drone airplane in Belgium though, the sound quality is extremely bad but it could be (something like, 'cos I don't know where this video was shot) this http://www.youtube.com/watch?v=FgAQUPkye88 I only heard the whirring but it might be that it drowned out the rest of the sounds the airplane made, or that it's another type, or whatever.

It's not much of a spy vessel if it's noisy enough to wake people right up though. But that's probably it, I think. It would also explain why it's not a constant thing you should always hear like electricity and only happens once in a while. Except if it's a sound transformed by the weather, that's possible too.

It was impossible for me to look for similar sounds without encountering many conspiracy theories / scam videos However right now we're pretty much convinced it's merely the new spy drone airplane they're testing out.

RoC77 wrote:It sounds like it might be a power transformer. Is there one near your house?

Yes, very close even, although it's been there since forever and the sounds are new. We've been having an unnatural amount of problems with many electric devices in the house, I wonder if it could be related?